earth arcing

[markysparky]

Removed a cpc from a ceiling rose because it looked like it wasnt terminated correctly, as i loosened the screw it arced!

Surely that is not right.Done a quick test and got 60v between e and n.

This is at my house which was a new build 3 years ago. Had no other probs. Any ideas what is causing this.

Will break down circuit and do full test on circuit tomorrow

 

[matt.leung]

you have some touch voltage. an earth conductor can carry up to 50v

 

[la poste]

you have some touch voltage. an earth conductor can carry up to 50v

Could you explain why?

Cheers.

 

[Robin Spark]

Removed a cpc from a ceiling rose because it looked like it wasnt terminated correctly, as i loosened the screw it arced! Surely that is not right.Done a quick test and got 60v between e and n.

This is at my house which was a new build 3 years ago. Had no other probs. Any ideas what is causing this.

Will break down circuit and do full test on circuit tomorrow

Was this with the cct disconnected or still live? If you left cct live as you thought it would be ok to retermintate cpc then there might be some current start to run down the cpc due to capacitance. Was the 60 v between earth and neutral measured from the disconnected earth?

You will probably find everything ok once everything terminated properly and just do your normal continuity/ insulation tests etc to show cpc is not broken anywhere.

 

[markysparky]

The circuit was still live at the time as it was only the cpc. It just surprised me as never seen that happen on a cpc before.

Will check circuit as got a new tester and wanted to get used to it.

 

[Sidewinder]

markysparky,

You said you have got yourself a new tester.

What make/model is it please?

Paul

 

[markysparky]

Sidewinder its a metrel 61557, got it from ebay. seems ok just takes a while to do rcd z's, 15 sec or so.

 

[Sidewinder]

Digital multifunction then.

Probably a very high input impedance. Could not find this specified anywhere it may be in the instruction manual, but this did not pop up in the quick searches I did.

Could be measuring 60V a.c. with a fractions of micro amps "behind it".

This could well be capacitive coupling from adjacent wiring.

Take a typical 10Mohms /V input impedance for a good digital meter, this wil very by make/model.

At 60V a.c. this would give the meter an input impedance of 60x10M = 600Mohms.

By ohms Law would give a current flow through the meter of 0.1 micro ohms.

Not a lot of current there, hence the term "phantom voltages" these are commonly measured with digital instruments.

 

[Evans Electric]

I usually suspect that the lighting earth wire is not actually connected to earth when stuff like that happens.

 

[Sidewinder]

Quite!

 

[Andy™]

if its arcing, then i would guess there is something leaking current to earth

and disconnecting a circuit earth whilst it is live is just plain stupidity

 

[Robin Spark]

[quote name='Andy

 

[Apache]

Even if there wasnt a fault on the cct wouldnt CFL's, electronic dimmers and transformers cause some leakage to earth in normal use anyway?

A CFL doesn't need an earth connection, nor do some class II dimmers - so no to them.

Couldn't say re transformers, but would have thought not?

 

[Andy™]

Even if there wasnt a fault on the cct wouldnt CFL's, electronic dimmers and transformers cause some leakage to earth in normal use anyway?

most lamp holders dont have an earth connection available for the lamp

and transformers only leak to earth incase of fault. most downlight transformers dont have an earth connection anyway